1. Field of the Invention
The invention relates to an apparatus for three-dimensionally displaying an object by casting stereo-images on an observer""s eyes, and also to a method of doing the same.
2. Description of the Related Art
Various apparatuses have been developed for three-dimensionally displaying an object. Three-dimensional display aims at reproduction of the same images as images obtained when a man observes an object, unlike planar display accomplished by a cathode ray tube (CRT). Three-dimensional display makes it possible to display an object approaching a spectator in a movie, or three-dimensionally grasp an object, which is difficult to grasp in a planar image.
Three-dimensional images we usually look at are established through focus control on which a distance to an object is reflected, convergence indicative of an angle formed by intersection between lines of sight of an observers eyes, and parallax indicative of a two-dimensional positional gap on images cast on observer""s retinas.
A conventional apparatus for three-dimensionally displaying an object is usually comprised of two cameras and a device for reproducing images. The two cameras are spaced away from each other by 65 mm which is equal to an average distance between a man""s eyes. In operation, stereo-images are taken by means of the two cameras, and the image-reproducing device casts images taken by the cameras on an observer""s eyes. As a result, parallax is generated on retinas of an observer""s eyes, and hence, three-dimensional display is accomplished.
FIG. 1 illustrates an example of a conventional apparatus for three-dimensionally displaying an object. The illustrated apparatus is comprised of a pair of image-displaying devices 101 located in front of an observer""s eyes for focusing images on an observer""s eyes, and a circuit 102 which provides image data to the image-displaying devices 101.
The image-displaying device 101 may be comprised of a cathode ray tube (CRT), a liquid crystal display, or a combination of an image-displaying device such as CRT and liquid crystal acting as a shutter. The image-displaying devices 101 form images in an observer""s eyes, or display images for right and left eyes frame by fame, and separate them by a liquid crystal shutter into right and left eyes of an observer. As a result, the image-displaying devices 101 form images having parallax to thereby accomplish three-dimensional display,
When an observer observes a three-dimensional object in actual space, the observer""s eyes recognize parallax, and at the same time, convergence is generated in the observer""s eyes in accordance with a distance between the observer and the object.
In a conventional method for accomplishing three-dimensional display by stereo-images, as mentioned above, two cameras positioned in parallel with each other are used, and images are taken so that they are focused on an object to be observed. Accordingly, convergence is coincident with parallax only when an observer observes an object which has been selected by the cameras as on-focus. Hence, if an observer who has observed only stereo-images so far observes an object other than objects having been selected as on-focus, a relation between parallax and convergence becomes quite different from a relation between parallax and convergence obtained when a three-dimensional object is observed in a usual three-dimensional space, resulting in a problem that coincidence cannot be made between images in the observer""s eyes.
There have been suggested various apparatuses for three-dimensionally displaying an object, as well as the apparatus illustrated in FIG. 1.
Japanese Unexamined Patent Publication No. 7-167633 has suggested an apparatus for three-dimensionally displaying an object, wherein minimum parallax in an observer""s eyes to an object is calculated, locations of reproduced images are calculated, and then, convergence points are determined so that the thus calculated locations of reproduced images are within a range of viewing angles of an observer""s eyes, based on results of the calculations. Optical axes of cameras are controlled in accordance with the thus determined convergence points.
Japanese Unexamined Patent Publication No. 8-166559 has suggested an apparatus for three-dimensionally displaying an object, comprised of monitor devices monitoring movement of eye-balls of an observer, a display device for two-dimensionally displaying images, a mover which two-dimensionally the display device, a lens, a calculator which calculates a gazing point of an observer""s eyes, based on the movement of eye-balls monitored by the monitor devices, and a controller which controls the mover to vary a location of the display device, based on the calculated gazing point.
Japanese Unexamined Patent Publication No. 8-211332 has suggested an apparatus for three-dimensionally displaying an object, which utilizes parallax of an observer""s eyes. The apparatus is comprised of means for determining an appropriate convergence angle in reproduction of images, and a controller which controls locations of reproduced images, based on the thus determined convergence angle. The locations of reproduced images are controlled by controlling a location at which image data starts to be written in a liquid crystal display.
Japanese Unexamined Patent Publication No. 8-234141 has suggested an apparatus for three-dimensionally displaying an object, including liquid crystal displays for an observer""s eyes Images having parallax are displayed in each of the liquid crystal displays to thereby accomplish three-dimensional display. In
use, this apparatus is put around an observer""s head. The apparatus is comprised of a device detecting a line of sight of at least one of an observers eyes, and determines a gazing point of an observer in an observing area, a image-processor which transmits an adjust signal by which a diopter is adjusted in dependence on parallax or convergence angle of images at the gazing point, and a motor for adjusting a diopter of the liquid crystal displays in accordance with the adjust signal.
Japanese Unexamined Patent Publication No. 9-218376 has suggested an apparatus for three-dimensionally displaying an object, comprising a distance calculator which calculates a distance to a gazing point, based on a convergence angle, a controller which determines a distance by and a direction in which image-displays and a focusing system are moved in order to move displayed images relative to an observer""s eyes with a size of displayed images being kept constant, and a driver which moves the image-displays and the focusing system in accordance with the decision made by the controller.
Japanese Unexamined Patent Publication No. 10-48569 has suggested an apparatus for three-dimensionally displaying an object, comprising image-formers which form two images having parallax, on image-presentation planes, a monitor which detects movement of an observer""s eye-balls to thereby obtain data about gazing point of the eye-balls on the image-presentation plane, a distance calculator which calculates a distance between the observer and an object located at the gazing point in images presented on the image-presentation plane, based on the data about gazing point, an adjuster which adjusts an convergence angle formed by lines of sight when the observer gazes at the object, based on the distance calculated by the calculator.
The above-mentioned conventional apparatuses for three-dimensionally displaying an object are common in that three-dimensional images are formed based almost only on parallax. If three-dimensional image is formed based only on parallax, it would be impossible to accomplish compatibility between parallax and convergence, which could be accomplished in natural observation. In general, since an observer does not always observe only on-focus locations, there is inevitable caused a problem that if an observer observers an object for a long time in the conventional method using stereo-images for three-dimensionally displaying an object, an observer""s eyes would be very tired.
In view of the above-mentioned problem in the conventional methods and apparatuses, it is an object of the present invention to provide an apparatus for three-dimensionally displaying an object, which is capable of accomplishing compatibility between parallax and convergence to thereby avoid an observer""s eyes from being tired. It is also an object of the present invention to provide a method of three-dimensionally displaying an object, which is capable of doing the same.
In one aspect of the present invention, there is provided an apparatus for three-dimensionally displaying an object, including (a) an area-identifier which detects a direction on which an observer turns at least one eye to thereby identify a display area at which the observer gazes, (b) a calculator which calculates, based on an image signal including parallax, a three-dimensional positional relation between the observer and an object to be observed, existing in the display area, and (c) an image-position controller which controls positions of images so that the object is displayed in the display area at locations on lines connecting the object located at a three-dimensional position calculated by the calculator, to centers of pupils of the observer.
In accordance with the above-mentioned apparatus, a three-dimensional distance is first determined between an observer and an object observed by the observer, based on information about parallax of the object and an interval between cameras. The used information about parallax is one of image information which is stereo-recorded by the cameras in the interval and certain convergence, and is displayed in the observer""s eyes. Then, the thus determined three-dimensional distance is divided by a distance between the observer""s eyes to thereby determine convergence which is to be generated when an observer looks at the object. Then, positions of images cast on the observer""s eyes are controlled in such a manner that convergence becomes equal to the convergence having been determined in the step (b).
A person""s eyes can receive much image-information therein. However, when eyes are focused on a common focusing point, a person can observe images, with high resolution merely within a maximum viewing angle of about 4 degrees. That is, though an area beyond a maximum viewing angle of about 4 degrees occupies almost all information received in an observer""s eyes, pixels displayed in such an area is fuzzy.
If convergence and parallax are coincident with each other at a gazing point, a person observing stereo-images can experience convergence associated with parallax, and hence, does not feel a sense of incompatibility between parallax and convergence unlike a conventional method or apparatus. As a result, the apparatus in accordance with the present invention makes it possible to much reduce an observer""s fatigue in observation of three-dimensional images.
It is preferable that the apparatus further includes an area-indicator which indicates a part of a displayable area as the display area and disallows an area in the displayable area other than the thus indicated display area to be displayed, in which case, the area is preferably located internally of an area in which there is displayed an image associated with convergence obtained when the observer looks at a point at infinity.
It is preferable that the display area is moved by inserting blank signals into original images at a right edge of the third area for a right eye of the observer and at a left edge of the third area for a left eye of the observer, the blank signals corresponding to an amount of horizontally moving pixel.
It is preferable that the image-position controller controls a position of an image so that parallax is zero at a center of each of retinas of an observer""s eyes associated with a gazing point.
There is further provided an apparatus for three-dimensionally displaying an object, including (a) image-displaying devices which display images at an observer""s eyes, (b) a beam scanner, (c) an area-identifier which detects a direction on which an observer turns at least one eye to thereby identity a display area at which the observer gazes, (d) a calculator which calculates, based on an image signal including parallax, a three-dimensional positional relation between the observer and an object to be observed, existing in the display area, (e) an image-position controller which controls positions of images so that the object is displayed in the display area at locations on lines connecting the object located at a three-dimensional position calculated by the calculator, to centers of pupils of the observer, and (f) a convergence generator which generates a difference between first timing at which the beam scanner is driven and second timing at which images start being displayed in the image-displaying devices, in accordance with a degree of convergence, and varies positions of images to be displayed in the image-displaying devices, in accordance with the thus generated convergence.
For instance, the convergence generator may be comprised of a memory storing addresses associated with positions of images displayed in the image-displaying devices, and a blank information writer which writes blank information into the memory, the blank information being information based on which a beam would not be generated, even if read out, in which case, the image-position controller indicates quantity and position of the blank information to the blank information writer.
There is still further provided an apparatus for three-dimensionally displaying an object, including (a) image-displaying devices which display images at an observer""s eyes, (b) a beam scanner including a scanning mirror for forming an image, (c) an area-identifier which detects a direction on which an observer turns at least one eye to thereby identify a display area at which the observer gazes, (d) a calculator which calculates, based on an image signal including parallax, a three-dimensional positional relation between the observer and an object to be observed, existing in the display area, (e) an image-position controller which controls positions of images so that the object is displayed in the display area at locations on lines connecting the object located at a three-dimensional position calculated by the calculator, to centers of pupils of the observer, and (f) a horizontally movable mirror which varies positions of images displayed by the image-displaying devices, in accordance with convergence.
For instance, the horizontally movable mirror may be located just at the rear of the scanning mirror.
It is preferable that the horizontally movable mirror is designed to be able to incline relative to an optical axis of the scanning mirror.
In another aspect of the present invention, there is provided a method of three-dimensionally displaying an object, including the steps of (a) determining a three-dimensional distance between an observer and an object observed by the observer, based on information about parallax of the object and an interval between cameras, the information about parallax being one of image information which is stereo-recorded with the interval and certain convergence, and is displayed in the observer""s eyes, (b) dividing the three-dimensional distance by a distance between the observer""s eyes to thereby determine convergence which is to be generated when an observer looks at the object, and (c) controlling positions of images cast on the observer""s eyes so that convergence becomes equal to the convergence having been determined in the step (b).
There is further provided a method of three-dimensionally displaying an object, including the steps of (a) detecting a direction on which an observer turns at least one eye to thereby identify a display area at which the observer gazes, (b) calculating a three-dimensional positional relation between the observer and an object to be observed, existing in the display area, and (c) controlling positions of images so that the object is displayed in the display area at locations on lines connecting the object located at a three-dimensional position calculated in the step (b), to centers of pupils of the observer.
It is preferable that a part of a displayable area is indicated as the display area in the step (a), and that an area in the displayable area other than the thus indicated display area is disallowed to be displayed, in which case, the area is preferably located internally of an area in which there is displayed an image associated with convergence obtained when the observer looks at a point at infinity.
It is preferable that the display area is moved by inserting blank signals into original images at a right edge of the third area for a right eye of the observer and at a left edge of the third area for a left eye of the observer, the blank signals corresponding to an amount of horizontally moving pixel.
It is preferable that the positions of images are controlled so that parallax is zero at a center of each of retinas of an observer""s eyes associated with a gazing point.
There is still further provided a method of three-dimensionally displaying an object, including the steps of (a) detecting a direction on which an observer turns at least one eye to thereby identify a display area at which the observer gazes, (b) calculating a three-dimensional positional relation between the observer and an object to be observed, existing in the display area, (c) controlling positions of images so that the object is displayed in the display area at locations on lines connecting the object located at a three-dimensional position calculated in the step (b), to centers of pupils of the observer, and (d) generating a difference between first timing at which beam scanning is started and second timing at which images start being displayed, in accordance with a degree of convergence, and varying positions of images in accordance with the thus generated convergence.
In accordance with the present invention, a relation between parallax and convergence is identical with the same obtained when a person actually observes an object. Hence, a person would not be tired regardless of observation of three-dimensional images for a long time.
In accordance with the apparatus including the beam scanner, since positions of images in right and left eyes can be varied merely by controlling timing at which the scanner starts to be driven and timing at which images start to be displayed, it would be possible to readily accomplish convergence.
Since the apparatus including the beam scanner does not have fixed dots unlike CRT and LCD, it would be possible to successively vary positions of images, that is, a degree of convergence. Hence, even when fluctuation in parallax is quite small, it would be possible to provide appropriate convergence accordingly.
Even when a liquid crystal display is used as the image-display device, convergence could be readily accomplished by confining a display area to a part of a displayable area of the liquid crystal display, and scrolling the thus confined display area horizontally and/or vertically.
The horizontally movable mirror may be located in front of a liquid crystal display, which would provide the same advantages as those obtained by the apparatus for three-dimensionally displaying an object, including a liquid crystal display.
The above and other objects and advantageous features of the present invention will be made apparent from the following description made with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the drawings.